Synthetic and/or resinous materials have been long used in flooring applications. Flooring materials such as floor tiles comprising vinyls, including polyvinyl chloride, are in use. Such flooring materials offer water resistance, low cost, mold-resistance and mechanical stability under common household and commercial application conditions.
Mass production of vinyl floor materials may use thermal molding of the vinyl material. Calendaring of sheet-like floor tiles is performed through the application of heat and pressure, and heat and pressure may be used in the surface smoothing process. To speed up manufacturing, methods of rapidly cooling to ambient temperature are used.
Fast cooling of vinyl materials, with or without other ingredients, especially in sheeting shape, impart a ‘thermal memory’ for the vinyl resin or vinyl thermoplastic materials that can change over time. In time the material will decrease in size along sheeting dimensions. When the temperature of the material approaches the softening temperature, even without substantial pressure applied to the material, shrinkage becomes a problem. Therefore, when vinyl flooring is used with processes where heat is applied above ambient temperatures, such as image transfer processes, undesired shrinkage results.
Thermal transfer imaging generally involves temperatures that are 350° F. or more. These temperatures are substantially above the softening temperature of the vinyl resins or thermoplastics. Shrinkage of more than 10% can take place, which substantially distorts the image quality, and reduces the physical dimensions of the flooring materials.
In order to assist thermal forming of vinyl/linoleum floor materials, plasticizers such as phthalates and other plasticizers are sometimes used. These plasticizers are liquid at ambient temperature, either in pure form or in a mixture with vinyl floor compositions, without chemically bonding. These plasticizers decrease thermal stability, and are colorant solvents. Slow evaporation overtime, and migration inside the flooring matrix, causes dissolution of the colorants by the plasticizers, which distort the image quality.
Thermoplastic materials such as polyvinyl chloride, polyvinyl acetate and the like often used in the floor tile to provide linear molecular structure suitable for thermomechanical molding. However, there is inadequate 3-dimensional stability required for a later heating process, such as is used with heat transfer imaging. This may be true even when the temperature and/or pressure of the flooring material fluctuates, either alone or in combination. Chemicals such as household cleaning materials, organic solvents, bleaching chemicals and enzymatic substances may also alter the polymer matrix of thermoplastic materials during usage.
To improve mechanical strength or durability, a top coating may be applied to the surface of the vinyl flooring material with inorganic filler particles, such as Al2O3 and SiO2. Without considering receptive properties or permeation properties, these coatings demonstrate poor thermal cohesive properties after the heat transfer imaging printing process is applied, largely due to the differences in the thermal expansion coefficient. The coating may also interfere with the image transfer.